Printing



. Patented July 24, 1934 PRINTING John Elton Cole, Wilmington, DeL,assignor to E. I. du Pont de Nemours & Company, Wilmington, Del., acorporation of Delaware No Drawing. Application January 25, 1938, SerialNo. 653,548

19 Claims.

This invention relates to the art of textile printing, and moreparticularly to the preparation of improved printing pastes and vat dyepastes. Specifically, it contemplates a novel type oi printing assistantfor use in pastes containing indigoid,

and especially thioindigoid dyes.

Textile printing differs from dyeing in that the color or colors appliedare confined'to certain parts of the material, thus producing differmcat designs or patterns. At the present time, the most extensive textileprinting is done with cylinders or roll printing machines. Thefundamental principles in this art are simple and comprise passing thecloth to be printed under some tension and pressure over an intagliometal roll, the engraving of which is filled with a printing paste.After leaving the printing machine, the printed cloth is passed into adrier. This dries the printing paste on the cloth in its proper placeand prevents the dye from spreading to other portions of the fabric. Inorder to complete the printing, the cloth, after leaving the drier, ispassed into a steam ager for a period of a few minutes, during whichtime the vat color undergoes reduction and passes to the fiber. Thefabric is then subjected to oxidizing conditions which may includepassing it into a steeping bath, usually of water or water containing anoxidizing agent. Any excess color is washed off in a soap solution withwhich the textile material is treated following the steeping.

The composition of vat dye printing pastes may vary widely withdiiierent dyes and manufactures, but usually consists of a mixture of anunreduced vat dye, a strong reducing agent such as, for example, sodiumhydrosulfite or sodium formaldehyde sulfoxylate, an alkali and athickening agent. The thickening agent is usually a gum (for instance,British gum), starch, or both. The printing paste is usually prepared bymixing a dye paste or pastes with the other ingredients, said otheringredients being in the form of a gummy mixture generally called aprinting gum. The dye pastes are essentially finely divided suspensionsof the dye, with or without a dispersing agent. In general, anysubstance which is responsible for results in textile printing whichshow an improvement over a water suspension dye paste may be called aprinting assistant. Printing assistants may be added to the dye paste orto the printing gum or to the printing paste, as desired.

It is an object of the present invention to produce improved results intextile printing. Other objects are to produce improved printing pastes,improved printing gums, improved dye pastes and improved printingassistants. and, in general,

to improve the art of textile printing. A further and more specificobject is to produce improved results in printing indigoid dyes, andespecially thioindigoid dyes. Other objects will appear hereinafter.

These'objects are accomplished according to the present inventionwhereby formates or compounds capable of yielding formates under theconditions of printing are used as printing assistants. These compoundsmay be used alone or in conjunction with other printing assistants.

While the invention is susceptible to considerable variation andmodification in the manner of its practical application, particularly asregards the nature and proportions of materials used, and the exactmethod of procedure, the following examples, in which the parts are byweight, will illustrate the practice of the invention.

Example I Twenty parts of a dye paste containing 10% formamide and 10%6:8'-diethoxy thioindigo were mixed with parts of a printing gumcontaining: 80

Parts Potash 9.1 Sodium formaldehyde sulfoxylate 6.6 Glycerine 10.0Thickener 54.3

The thickener employed was prepared by w ing:

Parts Wheat star h 1.0 British gum 3.0 Water 4.0 Gum tragacanth (6%solution) 1.0

The resulting printing paste was printed on a textile material anddeveloped in the usual manner. The prints were noticeably stronger andbrighter than those obtained from an exactly similar mixture without theaddition of the formamide.

Example II Twenty parts of a dye paste containing 10% 6': 6'-diethoxythioindigo and 10% sodium formats were mixed with 80 parts of a printinggum similar to the one mentioned in Example I, and this 5 mixture wasprinted on a textile material in the usual manner. The printing obtainedwas stronger and brighter than the one obtained from an exactly similarmixture in the absence of sodium formateu Example III.

Twenty parts of a dye paste containing about 12.5% of4:4'-dimethyl-6:6'-dichlor thioindigo and 10% of formamide were mixedwith parts of a printing gum and printed on a textile material in theusual manner. The resulting prints were about 10% stronger than thoseobtained from a similar mixture in the absence of the formamide.

Example IV Twenty parts of a dye paste containing 20% of5:5'-dichlor-'7:7'-dimethyl thioindigo and 10% formamide were mixed with80 parts of printing gum and printed on a textile material The printsobtained were about 10% to 15% stronger than those obtained from asimilar mixture in the absence of the formamide.

Example V Twenty parts of a dye paste containing 20% ofbis-beta-naphthionaphthene indigo and 10% of formamide were mixed with aprinting gum containing potash, sodium formaldehyde sulfoxylate andglycerine. The resultant mixture was printed on a textile material anddeveloped in the usual manner. The prints obtained were stronger thanthose obtained from a similar mixture without the addition of theformamide.

Example VI A printing gum was prepared by mixing together:

Parts Formami 4.0 Potash 9.1 Sodium formaldehyde sulfoxylate 6.6Glycerine 10.0

'I'hickener (having the approximate composition of that described inExample I) 50.3

The resultant product was incorporated with 20 parts of a 10% commercialpaste of 6:6'-diethoxy thioindigo, and the printing paste thus obtainedwas printed on a textile material in the usual manner. The printsobtained were stronger and brighter than those obtained from an exactlysimilar mixture in the absence of formamide.

According to procedures similar to those described in the examples,other dye pastes, printing pastes and printing gums, giving improvedresults in printing, may be obtained. Insofar as is known, theapplication of the invention gives improved results in printing anyindigoid dyes. Especially desirable results have been obtained inprinting the thioindigo dyes, such as those de scribed in the examples,and mixtures thereof.

The printing assistant preferably used in accordance with the inventionis formamide. It will be recognized, when vat dye pastes containingformamide are added to a strongly alkaline medium like'the printing gumsused in the art, that alkali formates and ammonia will most probably beformed. As a general rule, the salts of formic acid added to theprinting mixtures are as efllcient printing assistants as formamide onan equal molal basis. Where a formate is used as such, it is preferableto use thesoluble salts 1 of formic acid, particularly the alkali metalformates.

As already indicated; the assistants may be added advantageously to thecolor paste, or they may be mixed with the printing gum before or afterthe addition of the color. It is possible to add up to about 10% ofsodium formate, for instance, to a dye paste. Such a procedure is notvery practical, however, in most cases, due to the tendency of suchsemi-colloidal suspensions to iell upon the addition of salts.Therefore, when it is desired to add the assistant to the dye paste, itis usually found to be more convenient to add the formamide since it haslittle effect on the physical nature of the paste. In case it is desiredto add the assistant to the printing gum, it is generally moreconvenient to use the salts themselves. If sufllcient alkali is present,formic acid could equally well be used in the printing gum.

The amount of printing assistant may vary within relatively wide limitsbut may ordinarily be varied directly with the amount of dye. Empiricaltests can usually be made to determine the optimum amount of printingassistant for any given dye. Very satisfactory results are obtained withthe proportions of printing assistant described in the examples, butgreater or less amounts may be employed, if desired. If salts of formicacid are used directly in the printing gum, 1 there is practically nolimit to the amount which can be used without deleterious efl'ect. Ifformic acid or formamide is used, however, care must be taken that thereis suiilcient alkali present to neutralize the assistant and still bealkaline 11 ably be within the range of about 1.0% to about 1.

20.0%, on the basis of the weight of the dye paste. Especially desirableresults have been obtained in the use of about 10% of assistant, basedon the weight of the dye paste. v

The process of the invention gives particularly 1 valuable results withregard to the fullness and brightness of shade when the substratum uponwhich the color is printed is mercerized cotton. Good results may alsobe obtained in printing other cotton materials and, in general, mate- 1rials which may be printed with vat colors, including viscose rayon andother fibers, fabrics and yarns.

As previously indicated, the invention is particularly advantageous inthat the presence of 1 assistants of the character described in theprinting paste makes possible the production of prints of superiorstrength and brightness to those obtained from a similar printing pastefrom which the assistant has been omitted. The use of formamide is ofspecial advantage in that it may be incorporated directly with the dyepaste and has no harmful effect thereon, so that the resultant paste maybe marketed as such and reu quires only mixing with the printing gum foruse in printing.

Throughout the specification and claims it will be understood that theterm indigoid is intended to include not only indigo and dyes of theindigo series, but also thioindigo and other dyes of this type, as, forexample, dyes falling within the general formula and classificationgiven by G. von Georgievics and E. Grandmougin in A Textbook of DyeChemistry, 428, 1920).

As many apparently widely difierent embodiments of this invention may bemade without departing from the spirit and scope thereof, it

is to be understood that I do not limit myself to the specificembodiments thereof except as defined in the following claims.

I claim:

1. A dye paste comprising a water insoluble vat dye and a compoundselected from the group consisting of formates and substances capable ofyielding formates under the conditions of printi 8.

2. A printing paste comprising an unreduced vat dye and having anaddition thereto of a compound selected from the group consisting ofiormates and substances capable of yielding iormates under theconditions of printing.

3. A dye paste comprising a water-insoluble indigoid dye and a compoundselected from the group consisting of formates and substances capable oiyielding formates under the conditions ,of printing.

' unreduced indigoid dyes, said printing gum in- 8. A dye pastecomprising a water-insoluble thioindigoid dye and a compound selectedfrom the group consisting of i'ormates and substances capable ofyielding i'ormates under the conditions of printing.

9. A thioindigoid printing paste comprising an unreduced thioindigoiddye and having an addition thereto of a compound selected from the groupconsisting of formates and substances capable of yielding formates underthe conditions of printing.

10. A thioindigoid printing gum for use printing an unreducedthioindigoid dye, said printing gum including a compound selected fromthe group consisting of formates and substances capable of yieldingformates by reaction with an alkali.

11. An unreduced thioindigoid dye printing paste containing an alkalimetal formate.

12. A dye paste comprising an unreduced thioindigoid dye and formamide.

13. A dye paste comprising an unreduced thioindigoid dye and about 10%by weight or formamide.

14. A printing paste containing 6:6'-diethoxy thioindigo and an alkalimetal inmate.

15. A process which comprises printing textiles with a .vat dye printingpaste of the type in which the dye is originally water-insoluble, in thepresence of a formate.

16. A process of printing textiles which comprises adding to a pastecontaining a waterinsoluble indigoid dye and other customary ingredientsa compound selected from the group consisting of formates and substancescapable of yielding formates under the conditions of printing, andthereafter using the compounded paste in printing.

17. A process of printing textiles which comprises adding to a pastecontaining an unreduced thioindigoid dye and other customary ingredientsa compound selected from the group consisting of formates and substancescapable of yielding formates under the conditions of printing, andgiereafter using the compounded paste in print- 18. A process whichcomprises printing textiles with a printing paste containing anunreduced indigoid dye and an alkali metal formate.

19. A process which comprises printing textiles

